Where to buy credits in Rocket League?

I'm curious, where exactly can someone purchase credits in Rocket League? I've heard about the game's popular in-game currency, but I'm unsure of the best or most secure places to acquire them. Are there specific websites or platforms that are recommended for buying Rocket League credits? Additionally, are there any precautions I should take to ensure a SAFE and smooth transaction? I'd appreciate any insights you may have on this topic.